1. Field of the Invention
The present invention relates, generally, to effluent treatment apparatus for conditioning an effluent stream and, more especially, to effluent treatment devices such as air treatment apparatus where a conditioning agent is caused to interact with an effluent stream in order to condition the same prior to discharge to the ambient. Broadly speaking, the present invention may be used to good advantage for the "conditioning" of a "fluid effluent" by treatment with a "fluid conditioning agent" to "alter" the effluent, as defined more particularly herein.
2. Description of the Background Art
Numerous, diverse types of treatment apparatus have been devised over the last several decades for the conditioning of effluent streams, and particularly gaseous effluent streams, generated during industrial processes. A principal impetus for the development and use of such devices has arisen as a consequence of environmental conscientiousness in an effort to abate pollution. Thus, myriad designs have been proposed for the classification of particulate, the elimination of toxic, noxious or malodorous constituents, or the alteration (actual or perceptual) of the constituents of an effluent before it is released to the atmosphere. Experience has shown that the need to meet ever-increasing standards imposed upon those who must discharge an effluent stream to the atmosphere has resulted in the need to resort to very complicated and hence expensive machinery.
Various types of devices have been utilized to classify, segregate, or otherwise remove particulate material from a gaseous effluent stream. Conventionally, cyclone separators, electrostatic precipitators, so-called "bag houses" and plenum scrubbers have been employed for this task. Each type of device offers some advantage over the others but each has important limitations from either operational or cost-effectiveness points of view.
Conventional cyclone separators work fairly well for the classification of particles having nominal sizes greater than about 25-30 microns. As the particulate to be removed falls within progressively lower size ranges, the effectiveness of a conventional cyclone separator falls off precipitously. Typically, for particles less than about 10-15 microns, a normal cyclone separator is found to be virtually ineffectual.
Some have attempted to improve the ability of a cyclone to classify smaller particulates by the injection of fluid agents within the treatment zone of the device. The normative wisdom in this regard indicated that the fluid would effectuate an increase in the mass of smaller particulate thereby increasing the apparent size thereof insofar as classification is based upon centrifugal separation which, in turn, is directly related to the mass of the particulate to be classified. But, such prior attempts have normally diminished the overall operational efficiencies of the cyclone since the fluid injection has resulted in a diminution in field energy of the vortical flow of effluent-entrained particulate. By and large, therefore, there has been no development of commercially-acceptable wet cyclone devices.
Electrostatic precipitators are viewed to work very well for removing small particulate from an effluent gas stream. Nonetheless, complete commercial integration of electrostatic precipitators as a uniform mode of air treatment to remove particulate is unlikely to occur since these devices are quite expensive and, thus, cost-prohibitive for many applications. To a lesser extent, but equally applicable, are the sometimes prohibitive costs involved in the installation of bag houses.
Another approach for particulate removal is by means of a plenum scrubber. These devices rely upon the expansion of the effluent stream by introducing the flowing stream into a large chamber. The accompanying pressure drop tends to strip particulate from the effluent. Normally, fluid treatment agents are caused to pass in counter-current relationship vis-a-vis the direction of effluent flow. These devices are fairly efficient within fairly confined limits.
Oftentimes, it is mandatory to remove not only particulate but also to remove or treat undesirable fluid or gaseous components entrained within an effluent stream. Customarily, regardless of the device employed for conditioning the effluent, suitable chemical agents are included within a fluid caused to contact or otherwise interact with the effluent. Gases may be reacted for removal or adsorbed or absorbed on or within a liquid treatment agent. Fluids may likewise be reacted, mixed, coagulated, or otherwise altered sufficiently to effectuate removal from the effluent.
A persistent difficulty heretofore experienced in respect of the injection of fluid treatment agents within an air treatment apparatus results from limitations of the fluid injection devices employed. Quite routinely, fluid treatment agents, which usually must be finely dispersed to be optimally effective, are introduced via sintered nozzles having relatively small fluid passages. Other approaches, which attempt to minimize the need to use these fairly expensive sintered nozzles, nonetheless typically require discharge orifices of relatively small size in order to insure adequate atomization or dispersion of the fluid treatment agent. Virtually all such approaches result in the use of fluid injection nozzles highly prone to plugging if even very small sized foreign particulate finds its way within the fluid distribution system. This has all but eliminated the ability to use conventional filtration as a means for permitting recirculation of treatment fluid. Thus, the approach typically employed is to meter as best as possible the theoretical, optimum amount of treatment agent for reaction with the components in the effluent to be removed without including any excess. While this may seem fine on paper, in a plant many problems may be faced. If less than an appropriate amount of agent is injected into the air treatment apparatus, there will be incomplete reaction with the constituents to be removed and, accordingly, discharge of untreated effluent. If one attempts to compensate to insure virtually complete reaction, there is typically added an excess of agent which cannot be recovered and reused, contributing to an increased cost of operation and, perhaps, contributing to other sources of potential pollution since the remaining active components usually cannot simply be discharged to a sewer system.
Insofar as the present invention advantageously merges the concepts of certain prior art nozzles, adapting same specifically for use in conjunction with effluent treatment apparatus to overcome operational problems of the nature aforesaid, some background on the characteristics of these nozzles is appropriate. The class of nozzles involved are those which dispense a pressurized fluid, typically a liquid, through a flexible tube. As pressurized fluid flows through the tube and discharges therefrom, a reactionary force is felt within the tube wall. By carefully mating the wave mechanics of the flowing fluid with the mechanical properties of the flexible conduit, a standing or resonant flexural vibrational wave may be established in the tube itself.
This phenomenon has been recognized in various prior art devices where the flexural vibration of a tube is employed to some beneficial end. For example, irrigation or lawn sprinklers have been devised which rely on an oscillatory motion of a flexible tube when pressurized water discharges therefrom. Exemplary of such devices are those disclosed in U.S. Pat. Nos. 3,030,031 and 2,930,531. This general principle has also been applied to the atomization of a liquid, and a representative device for this purpose is disclosed in U.S. Pat. No. 3,123,302. Other nozzles where a spray is created by conveying a pressurized fluid through a flexible tube are disclosed in U.S. Pat. Nos. 2,417,222 and 2,758,874. The latter of these two patents is further noteworthy insofar as it discloses a means for controlling the spray by including an outer sleeve on the flexible tube which may be slid along the length thereof.
To date, the art has yet to appreciate that the general concept behind these oscillatory-type nozzles may be adapted to develop a nozzle which may be utilized in effluent treatment apparatus to overcome the serious limitations existing in these devices. Furthermore, the art has failed to appreciate that by suitable adaptation of such nozzles, the overall operational characteristics of many standard air pollution control devices may be materially enhanced.